Methyl oleate as matrix simulacrum for the simultaneous determination of metals in biodiesel samples by flame atomic emission spectroscopy

• A lab-made device was used to quantify simultaneously metals by emission spectrometry.
• Methyl oleate was used to prepare analytical curves for metal analysis in biodiesel.
• The procedure allows quantifying Ca, K and Na in biodiesel without pretreatment.

A measurement procedure for direct and simultaneous quantification of Na, K and Ca in biodiesel by flame atomic emission spectroscopy (FAES) was developed. A lab-made device was constructed by coupling a nebulizer/combustion system from a commercial photometer to a continuous emission detector in a spectral range of 255 to 862 nm. Instrumental optimizations were carried out evaluating the most important variables, such as gas flow rates and sample introduction temperature, indicating that a temperature of 50 °C enhances the analytical signals and assures good precision. The direct analysis method was properly validated and presented limits of quantification of 0.09, 0.07 and 0.43 μg kg−1 for Na, K and Ca, respectively. Accuracy of the proposed procedure was checked by comparing the results with those obtained by the standard procedure described in ABNT NBR 15556 and the standard addition method.

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